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Reprinted  from  the  Botanical  Gazette  45:  11 7-1 24,  Febniar    1908 

CALTFOP> 

Main  Mb, 
\"ric.   DtviL 

THE    ANTAGONISTIC    ACTION    OF    MAGNESIUM   AND 

POTASSIUM 

W.    J.    V.    OSTERHOTJT 

(with  three  figures) 

It  has  been  previously  pointed  out^  that  potassium  may  inhibit 
more  or  less  fully  the  poisonous  effects  of  magnesium  and  that  the 
abundance  of  potassium  in  the  soil  makes  this  inhibitory  action  of 
importance  in  soil  investigations.  Loew  and  Aso^  have  criticized 
this  statement.  Their  objections  are  that  only  chlorids  were  used 
and  that  no  flowering  plants  were  investigated.  In  the  present  paper 
these  objections  are  fully  met.  The  experiments  extend  over  a  wide 
range  of  forms  and  their  general  agreement  furnishes  conclusive  proof 
of  the  above-mentioned  action  of  potassium. 

The  technique  employed  has  already  been  described  in  previous 
papers  in  this  journal.^  The  material  was  placed  in  glass  dishes  con- 
taining 100-300'^'^  of  the  solution  and  was  covered  with  glass  plates  to 
exclude  dust  and  hinder  evaporation.  Water  twice  distilled  and  salts 
which  were  tested  for  purity  were  used  throughout.  The  results  given 
in  the  tables  are  in  all  cases  averages  of  several  series  of  experiments. 

The  first  experiments  were  made  upon  a  marine  alga,  Entero- 
morpha  Hopkirkii,  which  is  able  to  live  in  both  sea  water  and  dis- 
tilled water.  It  was  taken  from  the  sea  water,  rinsed  in  distilled 
water,  and  placed  directly  in  the  solutions.  The  solutions  used  were 
of  the  concentration  0.37 5 w,  which  has  the  same  osmotic  pressure 
as  the  sea  water  in  which  the  plants  naturally  grow. 

In  pure  MgCl^  .0375 w  they  lived  but  four  days;  in  pure  KCl  .0375  w 
seven  days;  while  in  distilled  water  and  sea  water  they  were  alive 
and  vigorous  at  the  end  of  twenty  days  when  the  experiment  was  dis- 
continued. It  is  evident  therefore  that  both  KCl  and  MgCl^  have  a 
poisonous  action. 

This  poisonous  effect  largely  disappears  if  we  mix  the  two  salts 

I  OsTERHouT,   University  of  California  Publications,  Botany  2:235.  1906. 
'  Loew  and  Aso,   Bull.  Imp.  Coll.  Agr.  Tokyo  7:395.  1907. 

3  OSTERHOUT,   Box.   GAZETTE  42:127-134.    1906;   44:259-272.    1907. 

117]  [Botanical  Gazette,  vol.  45 


272648 


ii8 


BOTANICAL  GAZETTE 


[FEBRUARY 


(MgClj  and  KCl)  in  proper  proportions.  In  the  mixture  100*=*=  MgCl, 
+40*^*^  KCl,  the  plants  were  alive  and  in  good  condition  at  the  end  of 
twenty  days,  when  the  experiment  was  discontinued.  It  is  evident 
therefore  that  in  the  mixture  of  magnesium  and  potassium  chlorids 
the  plants  live  five  times  as  long  as  in  pure  magnesium  chlorid  and 
three  times  as  long  as  in  pure  potassium  chlorid. 

TABLE  I 

Marine  Algae 

All  quantities  given  are  cubic  centimeters  of  o .  37SW  solutions 


Coltuie  solution 


KCl 

100  KCl      I 

40  MgCla  S 

MgCl, 

Distilled  water 

Sea  water  (total  salts = 2. 7  per  cent.) 
Artificial  sea  water  (total  salts  = 
2.7  per  cent.): 
100  NaCl  \ 

7.8MgCU    / 

a.SMgSO^J 

2.2  KCl       1 
I  CaCla         ' 


Duration  of  life  in 

days:    Entero- 
tnorpha  Hopkirkii 


7 
20  + 

4 

20+ 
20+ 


20+ 


The  plus  agn  indicates  that  the  plants  were  ali\-e  at  the  end  of  the  experiment. 

The  results  obtained  from  the  study  of  Vaucheria  were  even  more 
striking.  Zoospores  were  allowed  to  attach  themselves  to  slides. 
These  were  then  rinsed  in  distilled  water  and  placed  in  the  solutions. 
The  results  are  shown  in  the  following  table  and  also  in  ^^.  i. 

TABLE  II 
Fresh-water  Algae 
All  quantities  given  are  cubic  centimeters  of  .oiw  solutions 


i9o8]  OSTERHOUT— ACTION  OF  MAGNESIUM  AND  POTASSIUM  iig 

A  large  Spirogyra  of  the  majuscula  type  was  used  for  experiments 
with  the  stronger  solutions.    The  results  are  given  in  Table  III. 


TABLE  III 

Fresh-water  Algae 

All  quantities  given  are  cubic  centimeters  of  .0937W 

solutions 


0 


Culture  solution 

Duration  of  life  in  days: 
Spirogyra  species 

KCl 

i 

13 

100  KCl      I 

40  MgCla  S 

MgCla 

25  + 

Distilled  water 

The  plus  sign  indicates  that  the  plants  were  alive  at  the  end  of  the 
experiment. 

A  series  of  experiments  was  next  made  with 
the  gemmae  of  Lunularia.  These  were  allowed 
to  float  on  the  surface  of  the  solutions.  A 
large  number  was  used  and  the  average  results 
given  in  the  following  table. 

TABLE  IV 

Liverworts 

All  quantities  given  are  cubic  centimeters  of  .0937W 

solutions 


Culture  solution 

Duration  of  life 

in  days: 

genunae  of  Lunularia 

KCl 

12 

100  KCl      ) 

120  + 

so  MgCl,  ) 

100  KCl      I 

120  + 

100  MgCla  S 

50  KCl      ) 

100  MgClj  ) 

MgCU 

4 

Distilled  water 

<?. 


0 

3 


The  plus  sign  indicates  that  the  plants  were  alive  at  the  end  of  the 
experiment. 


Fig.  I. — Growth 
of  Vaucheria  during 
45  days  in  .  01m  solu- 
tions. I,  KCl,  gain 
o;  2,  ioqcc  KCl 
-I-40CC  MgClj,  gain 
4200%;  3,  MgCla, 
gain  o.     X  25. 


I20 


BOTANICAL  GAZETTE 


[FEBRUARY 


It  will  be  noticed  even  when  magnesium  greatly  preponderates  in 
the  mixed  solutions  the  plants  live  twenty-five  times  as  long  as  in  pure 
MgClj,  and  over  eight  times  as  long  as  in  pure  KCl.  Increasing  the 
proportion  of  potassium  increases  the  length  of  life. 

The  same  relation  is  seen  more  completely  in  the  next  table  (Table 
V).  Decreasing  the  amount  of  Mg  causes  increased  growth  up  to  a 
certain  point  (loo  K  +  io  Mg).  StUl  further  decrease  of  the  relative 
amount  of  Mg  beyond  this  point  is  imfavorable.  The  optimum 
relation  is  therefore  not  far  from  lo  Mg  +  loo  K. 

TABLE  V 

Liverworts 

All  quantities  given  axe  cubic  centimeters  of  .037SW  solutions 


CUVrtTKE  SOLUTION 


KCl 

100  KCl      ) 

5MgCla5 

100  KCl      I 
10  MgCla  S 

100  KCl      I 
25MgClJ 

MgCU 

Distilled  water 


Growth  in  150  days:  geioiae 
of  lunulakia 


Length  of 
thallus 


0-5 
3-3° 

3-41 

2.6 

o-S 
6.60 


Percentage  of 

gain  in  length 

of  thallus 


O 
560 

582 

420 


It  will  be  noticed  also  that  the  gemmae  made  no  growth  whatever 
in  pure  MgClj  or  pure  KCl,  while  in  mixtures  of  the  two  a  good  growth 
occurred. 

For  the  study  of  flowering  plants  wheat  was  chosen.  The  seeds 
were  supported  in  the  solutions  on  strips  of  filter  paper  as  described 
in  a  previous  paper.'*  The  results  agree  with  those  already  given. 
Table  VI  shows  that  certain  mixtures  of  potassium  chlorid  and  mag- 
nesium chlorid  are  much  more  favorable  than  cither  of  the  pure  salts 
(see  also  figs.  2,  j). 


4  0STERH0TJT,    BOT.  GAZETTE  44:259-272.    1907. 


i9o8]  OSTERHOUT— ACTION  OF  MAGNESIUM  AND  POTASSIUM   12 1 


^ 


1 


Turning  now  to  the  experiments  with  sulfates  and  nitrates,  we 
see  entirely  similar  results,  save  that  the  mixed  solutions,  while  better 
than  pure  magnesium  salts, 
are  not  better  than  pure  potas- 
sium salts.  The  question 
might  then  arise  whether  the 
favorable  result  is  due  in  this 
case  to  mere  dilution  of  mag- 
nesium salts  with  less  poison- 
ous ones.  This,  however,  is 
not  the  case.  We  are  dealing 
with  a  true  antagonistic  action. 
This  is  shown  by  the  fact  that 
addition  of  the  potassium  salt 
in  solid  form  likewise  pro- 
duces a  favorable  result,  and 
also  by  the  fact  that  the 
addition  of  pure  water  does 
not  produce  anything  like 
the  improvement  seen  on  the  addition  of  the  same  amount  of  a 
solution  of  a  potassium  salt. 

.0937  m 


Fig.  2. — Growth  of  wheat  roots  during 
40  days  in  .og^ym  solutions:  I,  MgClj, 
aggregate  length  of  roots  io""n;  2,  loocc 
KCl  +  2SCC  MgClj,  aggregate  length  of  roots 
153™™;  3,  KCl,  aggregate  length  of  roots 
no™™.   X§. 


.05  m- 


,037&m 

a  bed 

Fig.  3. — Curves  showing  growth  of  wheat  roots  in  salt  solutions.  The  ordinates 
represent  concentrations  (parts  molecular);  the  abscissae  represent  the  aggregate 
length  of  roots  per  plant  in  millimeters,  a,  loocc  KCl+ioocc  MgCU;  6,  loocc  KCl 
+  SOCC  MgClj;   c,  KCl;  d,  ioqcc  KCI  +  25CC  MgClj. 


122 


BOTANICAL  GAZETTE 

TABLE  VI 
Wheat 


[FEBRUARY 


Culture  solution 

Growth  during  60  days 
aggregate  length  of  roots  per  plant  dj  lof . 

In  .og37w  solutions 

In  .05  m  solutions 

In  .o3^sm  solutions 

KCl 

no 
66 

72 

153 

10 

80 

36 
48 
60 

4 

114 

12 

32 
80 

35 

268 
170 

224 

312 

20 

216 

112 

148 

166 
10 

275 
76 

144 

224 
8 

340 

loo  KCl      ) 

loo  MgCU  ) 

loo  KCl      \ 

294 

388 
28 

50  MgCla  S 

100  KCl      \ 

25  MgCl,  5 

MgClj 

SO  K,S04  I 

276 

144 

190 

240 
24 

50  H,0      S 

5oK,S04   ) 

100  Mgso^  5 

5oK,S04   ) 

SO  MgS04  ) 

SoKjS04    I 

25  MgS04  5 

MgSO. 

KNO, 

345 
104 

100  KNO3         ) 

100  MgCNOj),  J 

100  KNO3         ) 

198 

290 

10 

5oMg(N03),5 

100  KNO3         I 

2sMg(N03),i 

MeOSIO,), 

Distilled  water 

lAO 

Since  each  molecule  of  K,S04  yields  two  K  ions,  half  as  much  K.SO^  is  used  as  KCl  or  KNO, . 
The  figures  for  50  K.SO4+S0  H.O  are  comparable  with  the  corresponding  figures  for  KCl  and  KNOj, 
though  the  concentration  of  the  solution  is  only  half  as  great.  For  example,  the  roots  reach  a  length 
of  8o""»  in  so«  K,S04  .o937»»  +  soee  H.O;  a  length  of  216""  in  50"  K,S04  .osw  +  so"  H.O;  and 
a  length  of  276"™  in  50"  KaS04  .037sm+so«  H.O. 

It  will  be  noticed  that  these  antagonistic  effects  are  less  marked  as 
the  concentration  is  lowered.  This  is  of  course  true  of  all  antago- 
nistic action,  since  as  the  concentration  is  lowered  toxicity  diminishes 
and  the  effect  of  its  inhibition  is  consequently  less  striking. 

It  is  observed  that  those  parts  which  are  in  direct  contact  with 
solutions  always  show  their  effects  much  more  plainly  than  those 


1908]  OSTERHOUT— ACTION  OF  MAGNESIUM  AND  POTASSIUM   123 

(e.  g.,  leaves  and  stems)  which  are  raised  above  them.  It  seemed 
desirable  therefore  to  find  out  how  sections  of  stems  and  roots  would 
behave  in  the  solutions.  The  answer  to  this  question  is  given  in 
Table  VII.  Transverse  sections  of  the  stem  of  Tradescantia  and  the 
root  of  the  common  red  beet  were  employed.  They  were  cut  on  a 
microtome  and  were  of  considerable  but  uniform  thickness. 


TABLE  VII 

Cuttings  and  Sections 
All  quantities  given  are  cubic  centimeters  of  .o937ffi  solutions 


Culture  solution 


Duration  of  life  in  days 


Microtome  sections 

of  stem  of 
Tropaeolum  majus 


Microtome  sections 

of  root  of 

Beta  vulgaris 


Develophent 


Cuttings  IS'" 

long  of 
Tradescantia 


KCl 

ICO  KCl       ) 
40  MgCU  )  ■ 

MgCU 

Distilled  water. 


20 

28  + 

20 
28  + 


14 
27 

18 
28  + 


No  roots 

Short  roots 

No  roots 
Long  roots 


A  plus  sign  indicates  that  the  plants  were  alive  at  the  end  of  the  experiment. 

In  both  cases  the  color  and  microscopic  appearance  served  as  the 
criterion  of  death.  As  is  seen  in  Table  VII,  the  results  agree  with 
those  already  obtained.  The  table  likewise  shows  the  results  obtained 
from  cuttings  of  Tradescantia  (about  15'^™  long)  which  were  placed 
with  their  lower  ends  in  the  solutions. 

In  view  of  the  striking  agreement  of  results  obtained  from  such  a 
variety  of  material,  it  seems  useless  to  seek  for  further  proof.  The 
experiments  of  Loew  and  Aso  also  show  antagonism  between  potas- 
sium and  magnesium,  as  far  as  they  go.  They  do  not,  however, 
employ  sufficient  potassium  (nor  sufiiciently  strong  solutions)  to  bring 
out  the  results  clearly.  The  use  of  percentage  solutions  (rather 
than  molecular  solutions)  likewise  obscures  their  results.  More  funda- 
mental is  their  confusion  of  physiologically  balanced  solutions  with 
ordinary  nutrient  solutions.^ 

As  for  the  theory  of  Loew  and  Aso  that  the  inhibitory  action  of 
potassium  on  magnesium  is  due  to  the  formation  of  a  double  salt;  I; 

s  Cf.  Osterhout,  On  nutrient  and  balanced  solutions.  University  of  California. 
Publications,  Botany  2:317.  1907;  also,  BoT.  Gazette  44:259-272.  1907.       •*  *   .'. 


134  BOTANICAL  GAZETTE  [February 

need  merely  say  that  it  cannot  be  true  because  this  inhibitory  action 
is  seen  in  mixtures  of  potassium  nitrate  and  magnesium  nitrate  where 
no  double  salt  is  formed.  Moreover,  even  in  the  chlorids  and  sulfates 
the  formation  of  a  double  salt  cannot  much  affect  the  result,  since  the 
double  salt,  at  the  concentrations  here  used,  dissociates  and  sets  free 
magnesium  and  potassium  ions  to  almost  the  same  extent  as  the 
simple  salts. 

RESULTS 

Magnesium  salts  and  potassium  salts,  used  separately,  are  poison- 
ous to  plants,  but  when  mixed  together  (in  suitable  proportions)  the 
poisonous  effects  more  or  less  completely  disappear.  These  results 
are  of  importance  in  soil  investigations. 

•  University  of  California 
Berkeley 


/y 


